Pile foundations are typically used to support engineering structures where the surface soil is of poor quality. Often this soil is highly liquefiable when subject to seismic shaking. Lateral spreading, a phenomenon associated with earthquake-induced soil liquefaction, can impose particularly large lateral loads on pile foundations through the gross horizontal movement of liquefied soil. The interaction between the soil, piles, and superstructure, both during and after an earthquake, is inherently complex and many fundamental aspects of this interaction are not yet fully understood. This seminar explores the relationships between several fundamental design parameters (including pile spacing, and pile tip/cap fixity), the mechanism of soil-pile interaction, and the resulting foundation performance.

Centrifuge testing of idealised pile groups is the primary method by which the problem has been explored. The experimental programme was underway at the time of the recent major earthquakes in Christchurch, affording a unique opportunity to incorporate observations from the field into the design of the centrifuge models. This seminar compares the mechanisms of pile-laterally spreading soil interaction observed in the field and the centrifuge tests, considers the validity of common assumptions made in the design of physical models for piles in laterally spreading soil and indicates some potential consequences for seismic foundation design.